The pupillary reflex, which occurs when light is reflected by the retina out through the pupil of an eye of a human or animal is a well known phenomenon, and has been the subject of considerable research. Through this research, it has been found that diagnosis of some abnormal conditions and disease processes of the eye may be made by observing the pupillary reflex. For instance, where a slightly off-axis light source with respect to an observation point directly in front of the eyes is directed into eyes of a subject, a reflex from an eye with normal refractive properties will not return the reflex to the observation point. Rather, a faint, general illumination of the pupil will be observed due to scattering of light within the eye. However, in an eye with abnormal refractive properties, a portion of the reflex will be observed at the observation point, with the extent of the reflex and position of the reflex about the circumference of the pupil being indicative of various abnormal conditions in the eye. Additionally, cataracts, occlusions, foreign objects and other opaque or semitransparent matter may be observed due to light being blocked by these objects or opacities. Additional information that may be ascertained includes binocular status of the eyes.
In U.S. Pat. No. 5,632,282, filed Oct. 18, 1994 by Dr. S. Hutson Hay et. al., and which is incorporated herein by reference in its entirity, a reflex photometer and method is disclosed for observing the retinal reflex from eyes of a subject. In this patent, a camera having a CCD array is mounted directly in front of eyes of a subject, and a slightly off-axis light source directs a strobed, collimated beam of light into eyes of the subject. An image of the eyes is received by the CCD array and processed by a general purpose computer to locate the eyes and identify a number of disease or other conditions that may be present.
While the algorithms of the referenced patent worked well, there were some situations wherein the eye could not be located. Accordingly, it is one object of this invention to provide methods of locating the eye which are inherently more robust, locating the eye in a higher percentage of trials. As an additional object of the invention, algorithms are disclosed herein that are also more accurate, being more computationally intensive due to recent developments that have increased computational power of microcomputers.